1. Technical Field
The present invention relates to gas discharge light sources, and more particularly to a starter for a gas discharge light source
2. Related Art
Lamp starters may be used to start and operate gas discharge lamps. Gas discharge lamps include cathodes that may be filaments disposed inside a gas filled enclosure, such as a tube. The filaments are used to strike an arc in the enclosure to ionize the gas. Once ionized, the gas may form a plasma that generates light energy. Such starters may be formed with one or more electronic components. A lamp starter may be used to control the voltage and current provided to the lamp during startup and operation. Typically, the starter includes a preheat cycle and a start cycle. During the preheat cycle, voltage and current are supplied to the filaments to warm the gas. Once the gas is warmed, a voltage and current may be supplied to the lamp to strike an arc.
The duration of the preheat cycle prior to the operating cycle may be based on a predetermined period of time, based on a resistor with heating characteristics similar to a lamp, or a current or a voltage supplied to the gas discharge lamp. In addition, in one type of preheat circuit, the resistance of a filament of the lamp is determined by measuring a voltage (V) of the filament, and a current (I) through the filament. When the filament is heated to a pre-specified resistance (R=V*I), the preheat cycle is complete and the lamp enters the operating cycle.
An optimal preheat duration maximizes lamp life, however, with all of these types of preheat schemes, the starter uses some form of generic predetermined value of time, voltage, current, or resistance to determine the duration of the preheat cycle. Accordingly, the type of lamp used with the starter must be known and previously tested to determine the generic predetermined time, voltage, current, or resistance value to be used in the preheat cycle. In addition, variations in materials and manufacturing of gas discharge lamps makes the optimal preheat duration of a lamp vary significantly, even among lamps made by the same manufacturer with the same materials. Thus, an optimal preheat duration for one lamp may significantly shorten the life, or reliability of another similar lamp. Further, as a gas discharge lamp ages, the optimal preheat duration may vary, and may vary differently among different lamps. Accordingly, there is a need for a starter with a lamp specific preheat duration that is customized to the particular gas discharge light source used with the starter, even when the gas discharge light source was previously not known or tested to optimize operation with the starter.